The passive cooler is a low-tech alternative to the cooler, a construction that absorbs heat from interior spaces at a rate of 19.8°F (11°C) per second. It does not require power or any advanced materials, but will run out of fuel in 5 game days and must be restocked with 50 wood (the same as the build cost) to continue working.

Passive coolers cannot lower the temperature below 59°F (15°C), so they cannot preserve food like electric coolers, but they can protect your colonists from extreme heat. They require research to be built, though tribal colonies start with the research already completed.